Impact wrench control



Jan. 31, 1961 w. s. DALE ETAL IMPACT WRENCH CONTROL 5 Sheets-Sheet 1 Filed Feb. 26, 1959 Jan. 31,1961 w. s. DALE ETAL 2,969,660

IMPACT WRENCH CONTROL Filed Feb. 26, 1959 3 Sheets-Sheet 2 FIGJO IN V EN TORS wlLL|AM s.DALE By PHILIP R.HASKELL Jam 31, 1961 w. s. DALE ETAL 2,969,660

IMPACT WRENCH CONTROL Filed Feb. 26, 1959 3 Sheets-Sheet 5 FIGJI "l 5259 55 56 Se FGJZ FGJB

Flam I A TTORNEYS INIPACT WRENCHCONTRGL William S. Dale, Kingston, RLL, and Philip RfHaislgell,

Fairfield, Conn., assignors toiRenlington Arms Company, `Inc., Bridgeport, Connu, :t1-corporation of Belavware .Filed Feb. yzr, :1959, ser.Nq.' r795,353

6 claims. (eroi-+27),

This invention relates y. to power drivenimpact toi-.gne

wrenches and the'artof controlling the output .of such i111-k pact Wrenches. e

More specically this invention is concerned with the 1provision of an limproved compact attachment Adevice :for use with conven-tional rotary impact wrenches or-incorporated in new tools to selectively and accurately .control and limit lthe maximum torque applied to a .driven member.

Generally, most power impact vwrenches on the -market today have a maximum torque output which is above the .maximum required or desirablein the tighteningof some -of the nuts or bolts they are intended .to handle. vWhile this extra power is useful in removing frozen-o rruste d `fasteners, many times it `results in tightening sornefasteners to failure if the tool is applied too long. Slip clutches have been found inapplicable inthe solution of this. prob- 1em of limiting impact type torques applied tofasteners. .No satisfactory device has appeared whichoifersacom- `pact, wide torque range, accurate means .of infinitely controlling or limiting the torque applied to a fastenerdevice by a rotary k'impact wrench. In addition, presently known .tools `cannot be operated vin a reverse direction without elaborate resetting and recalibra-tion to the torque .control lunit.

It is an object of this invention to provide a novel effective device for selectively and accurately controlling the Ytorture applied to fastener devices by a rotary impact -tool over a wide range of torques.

It is another object of this invention to provide adevice as discussed vabove which will function without .adversely aifecting the horsepower of the overall'tool.

lIt'is another object of this invention to provide such Va device which is compact in size, light inweight, vsimple and reliable in construction.

It is -yet another object of this invention -torprovide a tool lwhich `is continuously and ininitely adjustable -to vany torque within wide limits Without any heavy or corn- .plicated tools, and which lwill function as aforesaid and becapable of immediate reversal of direction ofoperaltionwithout modiication or adjustment.

Other objects vand advantages Vwill appear in the following description, the appended claims and the y.accomlpanying drawings in which:

- Fig. l isy a longitudinal cross-sectional view of .one 'form of torque limiting device embodying features of the .present invention. l

Fig. 2 'is ,an 'end view of the device of Fig. l.

Fig 3 is a view of the other end of the-device of Fig.. 1.

Fig. -4 `is a side elevational view of the device of Fig. 1.

Fig. 5 is a transverse cross-sectional view taken on line 5 5 of Fig. 1.

Fig. 6 isa longitudinal cross-sectional view of a modifed version of a torque .limiting device embodying features. of thepresent invention.

i Fig. 7 is an end view of the device o fFig. 6.

Fig. `Sis 1a view ofthe other end vof the vdevice o t ice Fig. 9 is a transverse cross-sectional 'viewtaken on line 9--9 of Fig. 6.

Fig. 10 is aside view of a torque Vlimiting device as disclosed in 'this application showing its positional relationship to av conventional power impact 'wrench andthe "boltjornut-engaging socketl as used therewith.

Figs.' L11'-'1"4" a'1'ecorresponding'views showing yet `another `modified version `of :atorque limiting device emlgioclyingrfeatures 'of 'the presentinvention. 10v e Y "mayt'be'utilizedjas an Aattachrnent unit or built into pneu- The improvedv torquev limiting device of this invention matic or electric power wrenches as an integral com- 'ponent thereof. devicelmayibe utilzedin connection with` tools vofthevv general-'type disclosed bythe Pott US. j'fPa'tent No.` 2,I0'12`91-6, jssued August ,27, 1935, or ofthe generali-Uwe disclosed Lby the Disser -U.YS. 'Patent No.

2,608,1'18,'issued on August-2,6, 1952, or of the general type Adisclosed vby ,Jimerson U.S. Patent No. 2,814,277, issued 'November'26, 11957. The device of the present invention is Avybelieved to be va significant improvement over Lthe devices shown in the aforesaid I'Disser and `.limerson patents aswell as the Torreson'UiS. Patent No. 2,250,736,

`issued .luly"29, 1941.

Generally stated, the embodiment ofthe attachment,

illustrated in Figs. l5, utilizes 'a'tapered torsional mem- ;ber 4 which may he of solid or longitudinally laminated construction, the eifective'length and sectional modulus'of y' ,Which are variedby a sliding member 5.

'More particularly, referring to lthe drawings, "the nuymeral 1 indicates a housing which may be cylindrical vor substantially `cylindrical in forni.V At oney end of this :housingis xedly secured a plug or driven head .mem-

`ber ,2. "The driven head member 2 isprovided with .a

non-circularsocket 9 upon which force is applied for' the purpose yof tightening up a bolt, nut or the like as will appear in the following description. The device can ,be Vattached to an electric or pneumatic rotary impact wrench. A transverse circular plate 3 is rigidly Asecured in place immediately adjacent member 2. Member 3;is

`provided with a central circular opening which receives a short cylindrical extension at one end of a longitudinally disposed tapered torsion member 4. The other end of 'torsion member 4 is supported in a rotatabledisc 7'which is Vretained in an annular internal groove at one end `of lthe housing 1. Disc 7 is provided-with a square or rectangular opening therethrough which tits the rectangular 'cross' section of extension of the'tapered torsion'member 4.

Two sets of opposed circular apertures 11 are provided through the cylindrical surface of housing 1, each set of apertures in staggered relation to the other as will beLclear from Figure 1.

A movable plug element 5 is slidably received in the interior of thehousing 1 and is provided with a slot y6 therethrough to accommodate the maximum tapered `dimansion of torsion `member 4 and be positioned at variious axial posiiton's longitudinally ofthe housing. The element'S `carries in its peripheral surface two diametrically lopposedradial tapped holes or bores into which Amay be threaded machine screws 10 which in coopera- 'fion with the'fholes 11 in the housing provide aconvenient 'means for positively holding element 5 in one of its lpossible positions along the 'interior bore of housing 1.

'The extension vf8 ofv torsion member Yi1 is olf rectangular transverse cross-section and is frictionally Aengaged bya bolt or'znut engaging socket so that the driving forces may .be transmitted thereto to tighten or otherwise act upon -a bolt or nut.

The operational relationship ofl rotary impact wrench, torque limiting device, bolt engaging socket and lbolt is believed to beclear fromY the showing .flnfoperatiom witlrthe .element 45 ,secured inone otite axial positions by screws 10, the socket 9 is engaged by the driving member of a power impact wrench while extension element 8 is drivingly connected to a bolt or nut through a socket member, as S.

Upon operation of the wrench, the applied torque will initially be transmitted through element 9, housing 1, screws 10, element 5, torsion member 4, extension 8,

and socket S to the fastener. The fastener will `be rapidly tightened to the point under conventional power impact wrench operation at which continuous drive ceases and intermittent drive impulses or impacts commence due to the inherent operation of the impact wrenches. Up

to this point the torsion member has transmitted the torque from the wrench undiminished to the socket and Ifastener. However, as the fastener is set up more tightly, its resistance to the transmitted torque becomes increasingly greater. With this increase in the -fasteners resistance to turning, the torsion member begins to absorb, within itself, an increasing part of the turning energy which is now being delivered in impulses. This part of the absorbed energy is absorbed by torsional flexing of the torsion member. This energy which is resiliently o-r elastically 'absorbed by torsional flexing, of course, is returned by the torsional member through the tool anvil to the rebounding hammer. For a given selected position of element 5 and hence selected torsion quality for the torsion member, a point in the fastener tightening process will be reached at which the fastener is so tightened that its resistance to further turning becomes very great. Hence, since the energy of the repeated impacts or torque impulses received from the power wrench remain substantially constant, when the above point is reached, most of the energy of the torque impulse received from the wrench hammer is absorbed by torsional flexing of the torsion member and in effect a negligible fraction thereof is transmitted through the tors-ion member to the fasteners. At this point the torque applied to the fastener has been effectively limited for a given axial position of element 5 along the torsion member 4. It is also important to note that at this point of maximum resistance of the fastener and maximum energy absorption by exing of the torsional member, that the rotational and axial rebound of the hammer element of the conventional power wrench also reaches a maximum amplitude.

In conventional power impact Wrenches of the type which do not have a shutoff mechanism responsive to a predetermined hammer element rebound condition, the tool will continue to operate after the above discussed point of maximum energy absorption by the torsion member but no appreciable amount of energy will be transferred to the fastener. Under these conditions the rotary impact wrench is operated for a period of time corresponding to appreciable continued movement of the fastener and then terminated. This will result in the imposition of some general limit on the torque applied to tightened fasteners.

In conventional rotary impact wrenches of the type which have a shut-off mechanism responsive to a predetermined hammer rebound condition, the tool will be shut off when the predetermined rebound condition obtains, which will be directly controlled by the torsional characteristics selected for the torsion member. With this type tool termination of tool operation is automatic. It will be understood that by providing a tapered torsion member with variable effective length as shown in Figures l-5 a very wide range of torsion characteristics and hence torque limits can be covered with one small size torsion member which in turn controls the size of the torque limiting device. A reversal of direction of drive requires no adjustment or changes whatsoever andthe chan-ge in torque setting desired is easily and simply accomplished with a screwdriver. The holes in the housing can easily be provided with indicia showing the torque limit foreach setting of the element 5. A modified version of an improved torque limiting device embodying features of the present invention is disclosed in Figures 6-9. Outstanding features and advantages of this version are its compact size and infinitely variable selection of the desired torque limit. It also is capable of reversible operation without adjustment or modification.

Reference numeral 21 indicates an elongated hollow housing preferably of polygonal transverse cross section. Secured in one end of housing 21 is a driving head member 22 the transverse cross section of which is circular and fits into the interior of housing 21. Member 22 abuts inturned flange elements at one end of the housing 21 and is provided with a plurality of circumferentially spaced axially extending bores into which are fitted a plurality of elongated pins 24. The elongated pins are slidably supported in corresponding circumferentially spaced axially extending passageways through a sliding' block 25 which has a transverse cross section matching that of the interior of housing 21. The other ends of pins 24 abut a disc member 26 which is backed up by an annular end closure member 28 also slidably received and fitted into the interiors of the housing 21. Member 28 is the driven member and is locked in place by a radial screw 39 extending through the housing into a threaded bore in member 28. A threaded shaft 23 is journalled at one end in a bore in the inner transverse face of member 22 and at the other end in a bore through disc 26, passing through in threaded engagement with block 25. A spring detent acts between disc 26 and mernber 28 to eliminate play between the parts. The exposed end of threaded shaft 23 is slotted to receive and be rotated by a screwdriver or like tool. It will be observed that such rotation of shaft 23 axially positions the block 25 in the housing and varies the effective length of pins 24 as torque, transmitting elements.

In operation the modified device of Figures 6-9 functions essentially the same as that disclosed in Figures 1 5, the plurality of pins 24 acting as a series of torsion members in limiting the transmitted torque. In this` modification the driven member 28 transmits torque to the housing 21 which through its non-rotating t with sliding block 25 transmits torque thereto. The driving head member 22 is, as noted, rotatable with respect to the housing 21 and receives torque therefrom through the variable effective length of the pins 24 extending between the block 25 and the driving head member 22. Suitable indicia means can be provided to show the torque settings for each position of block 25. One way of doing this is the provision of a slot longitudinally arranged in the housing 21 with the desired scale marked along one sidey thereof to be read against an index mark on the peripheral surface of block 25.

I'l'lhe version of the device shown in Figures 11-14 is of similar construction and operates in a similar fashion to the earlier disclosed versions and utilizes a torsion member of laminated construction. It has been determined that there are advantages in making the torsion element such as 4. of -longitudinally laminated multileaf construction. This results in a greater deflection for a given torsional stress and will provide a torsion element of increased life under severe usage.

From a review of Figs. 12-14 in conjunction with the foregoing disclosure of the device as illustrated in Figs. l-lO, it will he apparent to those skilled in the art that the housing 51 is of the same general configuration and function as housings 1 and 21 of the other figures. The torsion element 52 of Figs. 12-14 performs the same general function as the torsion element 4 and plurality of torsion elements 24 in the devices of the other gures. It will also be clear that slidably adjustable .element 55 of Figs. 12-14 operates in a manner similar to element 5 of Figs. l-5 and similar to element 25 of Figs. 6-9. Element 59 is a circular collar unit frictionally slidably fitted on the exterior of torsion element 52. Element 58 is an annular plug element fitted into the rear of the housing and secured in place by machine screw 56. Threaded shaft 53 is rotatably secured in plug element 58 and is in threaded engagement with element 5S to move element 5'5 axially in the housing to vary the effective length of the torque-transmitting portion of element 52. An index mark on element 55 can be read against the scale Gil in the housing to set the variable effective length of element 52 accurately.

In this case the driven member 58 through its connection to the housing 51 transmits torque thereto and the housing 51 through its sliding but non-rotating connection with the adjustable element 55 transmits torque thereto. The adjustable element 55 is non-rotatably engaged with the torsion element 52 which by virtue of the slidable adjustment permitted element 55 constitutes a torsion bar of variable eiective length to transmit torque to the driving socket wrench or other element aiiixed to the exposed end of t-he element 52. The member 59 being rotatable in the end of housing 51 does not enter into the torque transmitting chain but does serve to bind the assembly together.

Having speciiically described two modifications of improved devices embodying our invention we desire to determine the limits of the invention according to the scope of the following claims.

We claim:

l. A rotary impact device comprising in combination, a housing, driving means on end of the housing, a driven element connected to the other end of said housing, a torsion member drivingly connected to said driving means and the driven element and having a continuously varied cross section, and means engaging said torsion member cooperating therewith to selectively vary the effective length and selectively utilize one cross sectional area of said torsion element and establish a desired limiting impact torque which can be transmitted from said driving means to said driven element corresponding to the cross section and effective length of the torsion member selected.

2. A rotary impact torque limiting device comprising in combination a housing, driving means mounted on one end of the housing, a driven element mounted at the other end of said housing, a plurality of torsion members in continuous driving engagement between said driving means and said driven element and manually operative means for selectively varying the effective length of said torsion members to determined the limiting torque which can be transmitted from said driving means to said driven element.

3. A reversible rotary impact torque limiting unit 5 comprising -in combination an elongated hollow housing, a driving member mounted at one end of said housing, a driven element positioned at the other end of said housing, a laminated torsion member continuously connected between said driving member and said driven element, said torsion member being of selectively variable unstressed spring characteristics to selectively determine and limit the maximum impact torque transmitted from said driving member to said driven member.

4. In a rotary impact tool of the class described, a driving member and a driven member inflnitely variable torsion spring means connected between said members for transmitting movement of the driving member to the driven member and means for selectively varying the effective elastic characteristics of said spring means so that it serves a substantially rigid connection lbetween said members so long as the force with which the driven member is moved below the corresponding value corresponding to the elastic characteristic selected and as an elastic connection whenever such force exceeds said corresponding value.

5. An impact torque limiting attachment for a rotary impact tool comprising an elongated hollow housing, a driving connector element rigidly secured at one end of said housing and adopted to be drivingly engaged with a rotary impact tool, a torsion means continuously drivingly engaged with said driving connector element, adjustable means cooperating with said torsion means to vary the effective length thereof to determine the maximum torque to be transmitted through the attachment, and a driven element in continuous driving engagement with said torsion means.

6. An impact torque limiting device for combination with a rotary impact wrench comprising an elongated hollow casing having a driving element rigidly secured thereto at one end, a tapered elongated resilient torsion member longitudinally supported in said casing for rotary motion therein, a driven element drivingly connected with one end of said torsion member, and a longitudinally movable block mounted in said casing to rigidly connect said casing to said torsion member at selected points along its length to determine selectively the maximum torque transmitted lfrom said driving element and casing to said driven element.

References Cited in the le of this patent UNITED STATES PATENTS 2,441,038 Siesel May 4, 1948 2,558,158 Rock June 26, 1951 2,822,677 Reynolds Feb. 11, 1958 

